AKsparky1
Member
- Location
- Anchorage, Alaska
I have four sets of 3c 350kcmil w/EGC feeding a 1200 amperes 480 volt panel. The wiring method is MCHL. These cables originate from a transformer outside and enter a modular constructed building erected with exposed steel including the floor. The cables terminate into TMC cable connectors and Myers hubs that are installed in the module floor deck plate approximately 18 inches below the 480 panel. The panel sits on the steel floor which has an opening in it to allow the conductors to pass through a chase into the enclosure. The design engineers detail suggests bonding the hubs with one #6 awg green insulated conductor from hub to hub then land the tail to a stainless steel bolt welded in the steel chase plate. Then run a 2/0 bare from the bolt into the panel and attach to the panel ground bus. in addition the design engineers suggest installing a #2 green insulated conductor from the enclosure (can) via bolt through to the module electrode connected to the verticle support mounts at the module base. This is a non hazardous classification.
250.97 Bonding for over 250 volts refers to 250.92 (B) except for (B1) tells us that we have to bond these hubs. 250.102(C) states to use table 250.66. 250.102(C2) size for parallel conductor installations in two or more raceways states to use Table 250.66 and looking at note 3 I would need to add four 350kcmil. 4X 350=1400kcmil then multiply 1,400.000 X .125 = 175 kcmil which is a 4/0. The #6 awg and the 2/0 in the design would appear to be undersized.
An RFI was written and a response stated the the grounding type Myers hubs are UL listed for up to a #6 awg and that Table 250.122 is the table to be using for the 2/0.
A 1200 amperes OCPD is downstream these feeders and if it was upstream then a 1200 amperes OCPD would require a minimum 3/0.
Do I need to get my head examined?
250.97 Bonding for over 250 volts refers to 250.92 (B) except for (B1) tells us that we have to bond these hubs. 250.102(C) states to use table 250.66. 250.102(C2) size for parallel conductor installations in two or more raceways states to use Table 250.66 and looking at note 3 I would need to add four 350kcmil. 4X 350=1400kcmil then multiply 1,400.000 X .125 = 175 kcmil which is a 4/0. The #6 awg and the 2/0 in the design would appear to be undersized.
An RFI was written and a response stated the the grounding type Myers hubs are UL listed for up to a #6 awg and that Table 250.122 is the table to be using for the 2/0.
A 1200 amperes OCPD is downstream these feeders and if it was upstream then a 1200 amperes OCPD would require a minimum 3/0.
Do I need to get my head examined?